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# to you under the Apache License, Version 2.0 (the
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#
#   http://www.apache.org/licenses/LICENSE-2.0
#
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from datetime import datetime
from typing import List, Optional

from sqlalchemy.engine.reflection import Inspector

from superset.db_engine_specs.base import BaseEngineSpec


class ImpalaEngineSpec(BaseEngineSpec):
    """Engine spec for Cloudera's Impala"""

    engine = "impala"

    _time_grain_expressions = {
        None: "{col}",
        "PT1M": "TRUNC({col}, 'MI')",
        "PT1H": "TRUNC({col}, 'HH')",
        "P1D": "TRUNC({col}, 'DD')",
        "P1W": "TRUNC({col}, 'WW')",
        "P1M": "TRUNC({col}, 'MONTH')",
        "P0.25Y": "TRUNC({col}, 'Q')",
        "P1Y": "TRUNC({col}, 'YYYY')",
    }

    @classmethod
    def epoch_to_dttm(cls) -> str:
        return "from_unixtime({col})"

    @classmethod
    def convert_dttm(cls, target_type: str, dttm: datetime) -> Optional[str]:
        tt = target_type.upper()
        if tt == "DATE":
            return f"CAST('{dttm.date().isoformat()}' AS DATE)"
        elif tt == "TIMESTAMP":
            return f"""CAST('{dttm.isoformat(timespec="microseconds")}' AS TIMESTAMP)"""
        return None

    @classmethod
    def get_schema_names(cls, inspector: Inspector) -> List[str]:
        schemas = [
            row[0]
            for row in inspector.engine.execute("SHOW SCHEMAS")
            if not row[0].startswith("_")
        ]
        return schemas
